Media Oriented Systems Transport (MOST) is a network configuration that employs a ring topology. MOST was developed for use within automobiles and is intended to provide a robust networking solution able to withstand the harsh operating environment that is characteristic of automobiles. MOST enables the seamless transport of digital audio, video, and packet-based data, and control information among multiple nodes in the network.
The MOST specification, for example version 2.4 as promulgated by the Most Cooperation of Karlsruhe, Germany, defines all seven layers of the ISO/OSI Reference Model for data communication. Within a MOST network, a Timing Master node (master) continuously feeds frames of data into the network or acts as the gate for data. The master generates frames of data at a rate that supports playback of CD quality audio data, DVD encoded video, and/or multimedia content within the MOST network. Other nodes within the MOST network are timing slave nodes that are synchronized by a preamble, which is located within a header portion of the frames.
Data within the MOST network is biphase encoded. Every bit is encoded as two biphase units, e.g., a pair of biphase units. Each new data bit starts, or is indicated by, a level transition in the signal. The level of the signal will change at the second biphase unit of a pair of biphase units that encodes a one bit. The level of the signal will remain the same for the pair of biphase units that encodes a zero bit. Again, the signal transitions at the start of each new bit.
Within a MOST network, data is organized into frames of 64 bytes. The frames are organized into blocks of 16 frames. The blocks are organized into super blocks of 64 blocks. In order to function properly, each node in a MOST network must acquire synchronization at the frame, block, and super block levels. As noted, nodes within the MOST network can maintain synchronization by identifying preambles of frames at expected locations. One characteristic of preambles is that each includes special biphase encoding.
When data is corrupted within a MOST network, a likelihood exists that the corrupted data will include a biphase coding violation. Portions of corrupt data within a MOST network data stream can cause the nodes of the MOST network to lose synchronization. Loss of synchronization can result in user perceivable dropouts in audio, video, or other content being played over the MOST network. When synchronization is lost, significant time and computing resources may be needed to re-acquire synchronization. This may further increase the length of any dropout(s) that occur during media playback over the network.